Force
What is the formula for force?
Force = mass x acceleration
What is the formula for momentum?
Momentum = mass x velocity
What is the formula for acceleration?
Acceleration = (final velocity - initial velocity) / time
What is the formula for weight?
Weight = mass x gravitational force
What is the formula for velocity?
Velocity = distance / time
If a horse pulling a 250 kg carriage accelerates at 4 m/s2, what is the force on the carriage?
F = ma
F = (250 kg)(4 m/s2)
F = 1,000 N or 1,000 kgm/s2
Which has the bigger momentum: a sportscar traveling at 60 miles per hour or an 18-wheeler truck traveling at 45 miles per hour?
The 18-wheeler because it is significantly heavier than the car, which makes up for its slower speed
What is the acceleration of a cheetah that can go from standing still to 30 m/s in 6 seconds?
a = (vf - vi)/t
a = (30 m/s - 0 m/s)/6 s
a = (30 m/s)/6 s
a = 5 m/s2
What is the value for the gravitational force on Earth?
9.8 m/s2
What is the velocity of an object that travels 150 meters in 3 seconds?
v = d/t
v = (150 m)(3 s)
v = 50 m/s
A little boy hits a tennis ball with 20 Newtons of force, and the ball then accelerates at 35 m/s2, what is the mass of the ball?
F = ma
20 N = (m)(35 m/s2)
(20 N)/(35 m/s2) = m
0.57 kg = m
What is the momentum of a 2,000 kg truck traveling at 45 m/s?
p = mv
p = (2,000 kg)(45 m/s)
p = 90,000 kgm/s
What is the final velocity of a falling ball, if it starts at rest and accelerates at 9.8 m/s2 in just 10 seconds?
a = (vf - vi)/t
9.8 m/s2 = (vf - 0 m/s)/10 s
(9.8 m/s2) x (10 s) = vf - 0 m/s
98 m/s = vf
What is the weight on Earth of a table with a mass of 10 kg?
W = mg
W = (10 kg)(9.8 m/s2)
W = 98 kgm/s2 or 98 N
What distance does an object traveling at 14 m/s cover in 5 seconds?
v = d/t
14 m/s = d/5 s
(14 m/s)x(5 s) = d
70 m
A track athlete throws a 0.8 kg javelin with 15 Newtons of force. What was the javelin's acceleration?
F=ma
15 N = (0.8 kg)(a)
(15 N)/(0.8 kg) = a
18.75 m/s2 = a
If a 55 kg sprinter has a momentum of 350 kgm/s, at what velocity is the sprinter running?
p = mv
350 kgm/s = (55 kg)(v)
(350 kgm/s)/(55 kg) = v
6.36 m/s = v
What is the initial velocity of a car if it decelerates at -2.5 m/s2 until it stops after 15 seconds?
a = (vf - vi)/t
-2.5 m/s2 = (0 m/s - vi)/15 s
(-2.5 m/s2) x (15 s) = (0 m/s - vi)
-37.5 m/s = -vi
37.5 = vi
What is the mass of an object that weighs 52 N on Earth?
W = mg
52 kgm/s2 = (m)(9.8 m/s2)
(52 kgm/s2)/(9.8 m/s2) = m
5.3 kg = m
How long does it take a horse running at 22 m/s to cover 100 meters?
v = d/t
22 m/s = (100 m)/t
(22 m/s) x t = 100 m
t = (100 m)/(22 m/s)
t = 4.55 seconds
A soccer player kicks a 2.6 kg ball with 55 Newtons of force. If the ball started from rest and took 2 seconds to reach its top speed after being kicked, what was its final velocity?
F=ma
55 N = (2.6 kg)(a)
(55 N)/(2.6 kg) = a
21.15 m/s2 = a
a = (vf - vi)/t
21.15 m/s2 = (vf - 0)/3 s
(21.15 m/s2)(2 s) = vf
42.3 m/s = vf
If a horse running at 21 m/s has a momentum of 19,950 kgm/s, what is the horse's mass?
p = mv
19,950 kgm/s = (m)(21 m/s)
(19,950 kgm/s)/(21 m/s) = m
950 kg = m
How long does it take a racecar to accelerate from a stop to 40 m/s if its acceleration is 8 m/s2?
a = (vf - vi)/t
8 m/s2 = (40 m/s - 0 m/s)/t
(8 m/s2) x t = 40 m/s
t = (40 m/s)/(8 m/s2)
t = 5 seconds
If an object that has a mass of 5.4 kg weighs 8.75 N on the moon, what is the force of gravity on the moon?
W = mg
8.75 kgm/s2 = (5.4 kg)(g)
(8.75 kgm/s2)/(5.4 kg) = g
1.62 m/s2 = g
If a sprinter runs at 0.5 km/min, what is her velocity in m/s?
0.5 km/min x 1000 m/km = 500 m/min
500 m/min x 1 min/60 sec = 8.33 m/s